The quality of recorded seismic data depends on many factors and a low signal‐to‐noise ratio leads to a low quality of processing and imaging. The zero‐offset common‐reflection‐surface stack and multifocusing methods have been successfully applied to improve the prestack signal‐to‐noise ratio by the partial summation of coherent seismic events. However, in the case of non‐hyperbolic traveltime behaviour of seismic events these approaches can result in non‐optimal partial summation. We develop a local common‐offset approximation for the traveltime stacking surface. It allows us to adequately approximate the traveltimes of reflection events in the vicinity of an arbitrary offset. Here, the stacking operator is interpreted as a local second‐order traveltime approximation of the seismic event and it is used for the purpose of partial summation. An algorithm and a numerical implementation scheme are discussed. The proposed signal enhancement procedure was applied to synthetic and real 3D data. Imaging results of the enhanced data show a high potential for reliable imaging in complex subsurface environments.

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We present in this work an exhaustive seismic study which was performed on a subset of a wide azimuth Ocean Bottom Cable seismic acquisition shot over a carbonate field from the U.A.E. A first challenge was to reprocess these data ensuring that the azimuthal information is properly preserved all along the sequence. An additional challenge is related to the very shallow water environment which brings complexity like dispersive ground-roll and water layer related guided waves, multiples which can be generated at sea-surface, sea-floor or internally, near-surface heterogeneities. On top of that the high velocities which are encountered in these carbonate formations are detrimental to a high resolution description of reservoirs. Two main issues are presented: Wide azimuth processing: the whole sequence was designed in order to preserve the azimuthal information. Multiples were attenuated in a cascaded approach including 3D predictive deconvolution and wide azimuth high resolution radon filtering. The Common Offset Vector strategy was followed at the imaging step to build 3D Common Image Gathers versus offset and azimuth, which enables to apply an azimuthally variant residual velocity correction and then stack all azimuthal contributions in an optimal manner. This azimuth friendly processing delivers gathers which are ready for azimuthal amplitude analysis. Heterogeneities and fracture characterization: we tested a newly developed technique for imaging diffractions and compared it to the azimuthal amplitude analysis performed on Common Imaged Gathers. This pilot processing study enabled to set up an operational wide azimuth processing sequence on this dataset, several processing scenarii could be tested and compared. In particular the sequence for attenuation of multiples was considered efficient, bringing a lot of character to the final result. The implementation of multi-azimuth Diffraction Imaging over this carbonate reservoir is proving very encouraging. Numerous detected features display geologically meaningful characteristics, some of them being not visible on conventional structural attributes. This study would be among the first applications of the methodology with tangible results providing more static and dynamic fracture data become available for calibration.